Reported equilibrium contact times by various researchers are 4 h for maize leaves [11], 20 h for polymeric Al/Fe modified montmorillonite [23], 6 h for waste iron slag [25], 22 h for iron impregnated potato peels [26] and 16 h for Fe-RHMCM-4 (DHT-10) synthesized from rice husk silica [27].